1. Field of the Invention
This invention relates in general to a load bearing bushing and, in particular, to an improved boat trailer bushing and method permitting gimbaling of roller supports on a boat roller shaft, suitable for bearing the load of a boat.
2. Background Discussion
In certain roller installations in support of boat structures, it is desirable to permit the roller to tilt relative to the boat roller shaft when the boat is being put in or hauled out of the water, thereby angling the roller structure relative to the center axis of the pin. Because of this pivotal motion, the roller moves in planes angled other than normal to the shaft, resulting in a gimbaling effect. The gimbaling effect allows the roller to engage the boat hull at an angle to facilitate the movement of the hull across the boat trailer. The gimbaling rotation of the roller is advantageous where a boat hull of varying design and shape is moved over the support rollers of the trailer and the like while loading or unloading the boat into or from the water. Even when a relatively large number of rollers are used to support the boat, it is desirable to have each roller self align to cause its tread to engage the hull across its full tread width, as compared to much smaller engagement along only an outer edge of the tread. A gimbaling roller thereby automatically self aligns and allows a full tread to follow and engage the changing contours of the hull and thereby minimize stress concentrations on the hull.
In U.S. Pat. No. 4,196,502, an insert member bearing bushing for a boat roller shaft was formed of two separate substantially identical washer or insert bearing members having curved sections. Each bearing member possessed an annular configuration and an approximately funnel like form with an inner peripheral curve section. The roller had to be structured with roller grooves adapted to receive each member. The prior art bearings were forced into the roller grooves to retain the bearing members inside the roller structure. The bearings could only be used with rollers that had special adapted grooves for the insertion of the bearing members. These bearings only supported the roller over a narrow surface area and resulting in a non-uniform load force being applied to the inner surface area of the roller, which could result in deformation of the roller. The deformation is magnified when the roller is tilted to its maximum, because the normal force of the load of the boat is not applied to the bushing, but instead had to be absorbed by the roller. This causes the roller to deform and contact the shaft, causing the roller to bind on the shaft.